Overview

The TwinCAT PLC library COMlib supplies function blocks and data structures for serial data communication. COMlib supports the serial Beckhoff KL6xxx bus terminal and the standard PC COMx interfaces.

The COMlib library is described in the document “COMlib PLC Library – Serial Data Communication”. The present document is to be seen as a supplement to that.

3964R communication

In addition to the basic functions of sending and receiving transparent data, COMlib3964R supports the 3964R protocol. The COMlib and COMlib3964R libraries thus replace the previous P3964lib library. Both libraries are included in the 3964R package.

The COMlib3964R communication library extends COMlib to implement an error-protected protocol for the transmission of any type of data. A checksum in combination with repetition of faulty telegrams provide the error protection.

RK512 communication

The RK512 protocol is used to transmit data blocks such as are used in Siemens controllers. The COMlibRK512 communication library uses the 3964R protocol for this purpose and handles the telegram traffic that it requires. The user only must parameterize the RK512 function block.

The "Serial Communication RK512" communication package contains all the necessary libraries. It supports the transmission of data blocks with a length of up to 128 data words.